'I'm A Celeb': Peter Rowsthorn shows off major body transformation after three weeks

It's been three weeks since the latest crop of Aussie B-listers entered the South African jungle for the fourth season of I'm A Celebrity...Get Me Out Of Here! and already the physical side effects are beginning to show.

Comedian Fiona O'Loughlin recently marvelled at the discovery of a long-lost hip bone, while top model Simone Holtznagel joked that her agent would find her "fabulously malnourished" upon exiting.

Forced to live off basic rations if they fail their "tucker trials", some contestants are embracing their skinny side, while others are using their jungle downtime to get buff.

Kath & Kim actor Peter Rowsthorn admitted that he was "a bit chubby" upon entering the show, but quickly put his efforts into a full time "Rocky Balboa style" training regime… and it's paid off, with the 55-year-old showing off his newly formed "four pack" in Monday night's episode.

With sporting heroes like AFL superstar Josh Gibson and boxing champ Danny Green as your trainers, you're bound to see some results.

"I love seeing the transformation in his body, in his mood," said resident fitness freak Gibson, who lovingly referred to his apprentice as "Rocky Rowsthorn".

"I'm just happy to be among elite athletes, pretending I'm one of them," joked Rowsthorn, adding, "I swear 1998 was the last time I felt this fit."

The father-of-four used his newfound physical prowess to earn meals for his campmates by completing a gruelling "plumbing" task while trapped in terrifying tank full of snakes, frogs, toads, and eels.

Eliminated contestant Kerri Armstrong, who selected Rowsthorn for the challenge, believes he has shown the most growth during his time in camp.

"The person who has come in here and is changing his life by being stronger and everyday doesn't stop, is Peter," she said in her exit interview, adding that as the oldest contestant, he's inspiring others to embrace their age and the strength that comes with it.

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